A strut is a type of damper that is used in vehicle suspensions as both a damping device for providing shock absorbing functions and as part of the suspension's load-bearing structure. Monotube gas-charged dampers are conventionally known wherein a piston with a connected piston rod is slidably carried in a fluid-filled tube with a separate piston called a gas cup slidably carried in the tube on an opposite side of the piston from the rod. The gas cup separates a compressible gas charge from the fluid within the damper. It is known that monotube gas-charged dampers exhibit desirable performance characteristics when used in some suspension assemblies.
Typically, the generic monotube strut design configuration is produced primarily as an aftermarket replacement damper, although limited original equipment (OEM), applications have been implemented. The prior art device generally includes a bearing mechanism that includes a combination of a polytetrafluoroethylene laminated plain bearing and a grease lubricant. In some applications performance advantages of high pressure monotube dampers are well known and therefore, the use of such devices without restriction would be desirable. However, in applying a monotube gas-charged strut in an OEM application, extended durability requirements lead to restrictions in the use of such devices, particularly in applications involving larger and heavier vehicles that operate with resultant increased side loading. In general, such limitations are related to two fundamental requirements that must be achieved before a monotube strut can meet expected OEM frictional levels and durability goals. First, the bearings must be assembled and maintained in a straight and true fashion in order to obtain acceptable friction levels. Second, the bearing lubricant must be effective and must be supplied to the sliding tube and bearing interface continually during operation of the strut. Accordingly, problems in filling these requirements must be solved in applying a monotube strut to widespread use in OEM applications.